As the most widely used medium-and-low temperature refrigerant at present, R22 is extensively applied in household air conditioners, commercial air conditioning, central air conditioning, portable air conditioners, heat pump water heater, dehumidifier, frozen-type dryer, cold storage, food refrigeration equipment, Marine refrigeration equipment, industrial refrigeration, commercial refrigeration, refrigeration condensing units, supermarket display cabinets and other refrigeration and air conditioning equipment. R22 (with its chemical name being chlorodifluoromethane) falls into the classification of HCFCs, possessing an ozone layer depletion potential (ODP) of 0.055 and a global warming potential (GWP) of 1700. Besides its depletion to the ozone layer, R22 also has a high greenhouse effect. According to the requirements of the Copenhagen amendment to Montreal Protocol on substances that deplete the ozone layer, R22 can only be used as a transitional working medium. Therefore, the developed countries will be required to fully eliminate the use of R22 by 2020 and the developing countries will be fully banned from using it by 2030. The EU has a made a faster move to have banned the import of HCFCs and the refrigeration and air conditioning equipment containing HCFCs since 2015.
At present, there are a lot of R22 units still in use in the market, and even large quantities of new R22 units are being manufactured each year for use. Under this situation, in the countries or regions where the HCFCs substances have been reduced or eliminated, the cost for maintaining and repairing the R22 units in service or replenish refrigerant wherein is very high. After 2020, the developed countries will totally face the problem of maintaining R22 units. And after 2030, the developing countries will also face such a problem. If the units are eliminated or replaced simply because the charged refrigerant does not meet the requirements of environmental protection, it will result in a waste of a large amount of resources and require the investment of a large amount of capital. Therefore, it is of significant importance to research and develop an alternative refrigerant which is not only compatible with the existing R22 units and can be used in mixture with R22 refrigerant, but also can be charged directly into the units in service and is in line with the laws and regulations with respect to the current refrigerant applications.
The existing single component refrigerant alternatives to R22 such as R32, R125, R143a, R134a and others cannot be directly charged into the existing units to replace R22. And the existing commonly-used blended refrigerant alternatives, such as R410A (a blend of R32 and R125), R407C (a blend of R32, R125 and R134a), R404A (a blend of R125, R143a and R134a), and R507A (a mixture of R125 and R143a), are incompatible with the working pressure and lubricant of R22 system, hence they cannot be charged directly into the units in service to replace R22. Moreover, substitutes such as R417A (a mixture of R125, R134a and R600), R422D (a mixture of R125, R134a and R600a) and others which have been developed specifically for R22 have shown a low efficiency and poor refrigeration performance after being used in the existing units to replace R22. In addition, the patent application US 2008029733 disclosed a composition consisting of pentafluoroethane, tetrafluoroethane and hydrocarbons and others; the patent application CN 200710156803.6 disclosed a composition consisting of R161, R32 and hydrocarbons and others; the patent application CN 93102698.9 disclosed a composition consisting of R32, R134a and one of the R152a, R143a and R290 and others; the U.S. Pat. No. 6,783,691 disclosed a composition consisting of R32, R125, R134a and hydrocarbons; the U.S. Pat. No. 5,624,596 disclosed a composition consisting of R32, R125 and hydrocarbons. These compositions mentioned in the above patent publications have all been developed for the purpose of replacing R22, but these compounds have such problems of either being incompatible with R22 system, or of low refrigeration efficiency, or being expensive and costing high replacement expenses.